Viscous-pendulum-damper



Jan. 27, 1970 w. H. REED m -DAMPER VISCOUS-PENDULUM Original Filed Feb.26, 1965 3 Sheets-Sheet l INVENTOR WILMER H. REED,I|I

ATTORNEYS Jan. 27, 1-970 w R5504 VIscOUs-PENDULUia-DAMPER Original FiledFeb. 26, 1965 3 Sheets-Sheet 2 FIG. 4

ATTORNEYS JanQZJ, 1970 w. H. REED m 3,491,857

' I 3 Sheets-Sheet 5 Original Filed Feb. 25. 1965 I INVEN'I'OR WILLMERH. REEDJJI BY ii-@1 1 ATTORNEYS United States Patent 3,491,857VISCOUS-PENDULUM-DAMPER Wilmer H. Reed Ill, Hampton, Va., assignor tothe United States of America as represented by the Administrator of theNational Aeronautics and Space Administration Continuation ofapplication Ser. No. 581,128, Aug. 8, 1966, which is a division ofapplication Ser. No. 435,756, Feb. 26, 1965, now Patent No. 3,310,138.This application Mar. 28, 1968, Ser. No. 717,052

Int. Cl. F16d 63/00 US. Cl. 1881 13 Claims ABSTRACT OF THE DISCLOSURE Avibration damper in which a mercury filled pendulous bladder mass islocated in a viscous fluid. The pressure in the bladder is remotelyvariable to alter the size and thus the dampening characteristics. Inother embodiment, the tubular container damper has a plurality ofscalloped tray sections filled with viscous liquid, each section havinga slug mass therein to dissipate energy.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

This application is a continuation of Ser. No. 581,128, filed Aug. 8,1966, now abandoned, which in turn, is a division of Ser. No. 435,756,filed Feb. 26, 1965, now U.S. Patent No. 3,310,138.

This invention relates generally to vibration damping and moreparticularly to a viscous pendulum damper having linear dampingcharacteristics.

Tall, slender structures such as towers, smoke stacks and space vehicleserected on the launch pad are susceptible to wind induced bendingoscillations. In a steady wind these oscillations are a result ofaerodynamic forces associated with vortices shed from the body andnormally occur in a plane perpendicular to the wind direction. It is notuncommon for the magnitude of these oscillatory loads to exceed, by afactor of five or more, the loads associated with the steady drag forcesof the structure. Thus, in order to insure that a structure is capableof surviving wind induced oscillations, wind tunnel investigations onaeroelastically scaled models are usually conducted prior to erection ofthe full scale structure. One of the key parameters which governs themagnitude of wind induced oscillations is damping, the capacity of astructure to absorb energy. In order to obtain meaningful data from windtunnel studies of the problem, it is highly desirable that the dampingin the model be varied to cover arrange of values likely to be found onthe full scale article. Investigation of the effects of internal dampingon response of a structure is particularly significant in the event thataerodynamic damping becomes negative at some critical wind speed. Insuch cases, wind tunnel data can indicate the amount of damping in thefull scale structure required to avoid possible catastrophicoscillations.

Prior methods of varying the damping of aeroelastic ground wind loadmodels in a controlled manner have in general been unsatisfactory. Thesemethods include varying the tension in joints on the model, connectingwires from the model to a dashpot damper or coating the structure withan energy absorbing material. Various difliculties are associated witheach of these methods; for example, damping variations obtained byadjusting the tension of bolts in a joint are unpredictable and arelikely to change during the course of a test run, the attachment ofexternal wires to the model presents aerodynamic interference problemsand energy absorbing coatings tend to be relatively ineffective unlessapplied to the model in regions of high strain. Furthermore, thesemethods of adding to a structure frequently exhibit nonlinearcharacteristics which greatly complicate the interpretation ofexperimental data obtained.

To overcome the above noted difliculties, the present inventioncontemplates the use of a pendulum-like member which reacts againstmotion of a viscous fluid to dissipate energy and thereby dampvibrations.

It is an object of this invention to provide a vibration damper havinglinear damping characteristics and bidirectional operation while beingcapable of precise regulation.

Another object of the instant invention is to provide a viscous pendulumvibration damper for tuned or untuned operation.

The further object of this invention is to provide a remotely controlledviscous pendulum damper.

Still another object of this invention is to provide a vibration damperwherein tray supported slugs act against a viscous fluid to dissipateenergy.

A still further object of the instant invention is to provide anexpandable pendulous mass for relative motion with a viscous fluid todamp vibrations of a primary body.

It is an object of this invention to provide a viscous vib'ration damperhaving a plurality of interfitting trays filled with a viscous fluid toreact against disc-shaped slugs disposed on the trays.

It is a further object of this invention to provide a vibration dampercomprised of one or more modules made up of a plurality of interfittingtrays having slugs disposed thereon to react with a viscous fluidfilling the tray member.

Still another object of this invention is to provide a viscous damperfor opposing the oscillatory motions of smoke-stacks and the like byutilizing a tubular container in the form of an arc of a circle with afluid substantially filling the container to act against a plurality ofspherical masses disposed therein.

Generally, the foregoing and other objects are accomplished by locatinga pendulous mass in a viscous fluid. For example, slugs may bepositioned on trays having spherically concave upper surfaces and whichare positioned within a container substantially filled with a viscousfluid or an expansible bladder may be connected to mercury filledbellows by means of a tubular member inside a container substantiallyfilled with a viscous fluid. By altering the number. of slugs, or byvarying the pressure activating the mercury filled bellows to therebyvary the size and weight of the expansible bladder, the dampingcharacteristics are altered. In the latter situation, a conduit mayconnect a remote controller with actuator bellows for varying thepressure on the mercury filled bellows to establish a remotelycontrolled viscous pendulum damper.

A more complete app eciation of the invention and many of the attendantadvantages thereof will be readily apparent as the same becomes betterunderstood by reference to the following description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of one embodiment of the instantinvention;

FIG. 2 is a cross-sectional view taken on line 22 of FIG. 1;

FIG. 3 is a cross-sectional schematic of an alternative embodiment ofthe instant invention;

FIG. 4 is an elevational view of a structure utilizing an alternativeembodiment of the instant invention;

FIG. 5 is a plan view of the embodiment of the instant invention shownin FIG. 4;

FIG. 6 is a partial elevational view of the embodiment of FIG. 4 showingthe quantities necessary for determining the tuned or untuned operationof the embodiment of FIG. 4;

FIG. 7 is an elevational sectional view, with portions omitted forclarity, of a further embodiment of the instant invention;

FIG. 8 is a top view of the embodiment of the instant invention shown inFIG. 7, again with portions omitted for clarity;

FIG. 9 is a bottom view of the embodiment of FIG. 7 with portionsomitted for clarity; and

FIG. 10 is an elevational detail view of a portion of the embodimentshown in FIG. 7.

Referring now to the drawing and more particularly to FIG. 1, whereinone embodiment of the instant pendulum damper, generally designated byreference numeral 10, is shown as having base 12 with a plurality ofperipherally spaced apertures 14 therethrough, Although shown as beingcylindrical, container 16 may be of any cross-sectional configurationthat has a cross dimension less than the distance between opposedapertures 14. Brackets 18 are secured adjacent the end of container 16opposite that to which base 12 is secured. Tray assembly 20 is sodimensioned as to fit within container 16 and includes vertical posts orsupport members 22 to which trays 24 are secured for supportingellipsoidal slugs 26. Viscous liquid 28, for example, a silicon fluid,substantially fills container 16 and encompasses tray assembly 20 toprovide a viscous liquid cover for all of slugs 26 on each of trays 24.

Container 16 is sealed by cover assembly 30 including flange ring 32rigidly secured thereto. Upper cover plate 34 is provided with aplurality of peripherally spaced apertures 36 for receiving screws 38extending into flange ring 32 for attaching cover plate 34 securely toring 32 andholding seal 40 in position. Trays 24 have a sphericallyconcave upper surface that is substantially symmetrical aboutlongitudinal centerline 42 of container 16. The spherically concaveupper surface of trays 24 permit slugs 26 to slide on the surfacethereof so that in effect the slug behaves as though it were a bobweightof a pendulum which has freedom to move in substantially any horizontaldirection.

Referring now to FIG. 3 wherein an alternative embodiment of the instantinvention is shown with remotely controlled viscous pendulum damperdesignated 60. This embodiment includes container 62 having a flange 63adjacent the open end thereof to provide a cup-shaped member. Cover 64is provided with substantially centrally located orifice 66 and aplurality of peripherally spaced apertures 68 that receive bolts 70 forsecuring top 64 to flange 63 of container 62.

Pendulum bladder 72 is preferably formed from an expansible material,such for example as neoprene or fibrous rubber, and is attached toflexible tube 74 mounted on divider 76. Divider 76 is provided with aplurality of orifices 82 to establish communication between lowerchamber 78 and upper chamber 80 formed in container 62 by divider 76.Actuator bellows 84 are attached to top 64 at one end and to mercuryfilled bellows .86 at the other end with bellows 86 being secured todivider 76 about the opening therein providing communication betweentube 74 and the bellows. Diaphragm 88 is located at the juncture ofbellows 84 and bellows 86 to react against both the mercury in bellows86 and return spring 90. Viscous liquid 82 fills lower chamber 78 andpartially fills vented expansion chamber 80 with orifices 82 permittingflow of fluid 92 between the two chambers upon expansion of pendulumbladder 72. Baflies 94 are secured to top 64 and extend downwardly intoupper chamber 80 to act with orifices 82 in eliminating slosh motions ofdamping fluid 92.

Conduit 96 is attached to tgp 64 about orifice 66 by a conventionalconnection (not shown) and extends to a regulated pr ssure sourcedesigna ed a remote p ssu e controller 100 which is of conventionalconstruction and accordingly a description thereof is unnecessary. Inorder to accurately determine the pressure in conduit 96, pressure gage104 is inserted therein near controller 100. The damper performance isdependent on viscosity of damping fluid 92 which is affected to someextent by temperature. Accordingly, thermocouple 102 is mounted incontainer 62 and utilized to permit calibration of damping withtemperature.

FIGS. 4-6 show an alternative embodiment of the instant inventivedamper, designated 160, and adapted for use with a smokestack, or otherelongated body 172. Damper 160 includes tubular container 162 thatdepends from support 164 attached to body 172. Tubes 162 are scallopshaped and conform approximately to the arc of a circle along theirlower edge to provide a support surface for spherical pendul-ar masses166 to give them a pendular movement against viscous fluid 168 whichsubstantially fills tubes 162. As in previous embodiments of the instantinvention, masses 166 act against viscous fluid 168 to dissipate energyand thereby dampen the oscillatory motion of body 172. Although shown inFIG. 4 as having three tubes 162, it is readily apparent that any numberof such tubes may be utilized depending upon the magnitude of the forcesbeing dampened. Fluid valves 176 are located in tubes 162 to provideaccess to the interior thereof for permitting changes of the viscousfluid or additions or removals thereof.

The number of spherical masses 166 and the number of arcuate deflectionsor scallops of tubes 162 may be varied in order to provide either tunedor untuned operation of damper 160. Referring to FIG. 6, smokestack orbody 172 is shown as being symmetrical about centerline 174 and in thisinstance is cylindrical having radius 178. Plane 170 extends through thecenter of spherical masses 1 66 and forms angle 0 with a line at rightangles to centerline 174. In order to design damper 160 for tunedoperation the skilled artisan will readily recognize that the pendulumfrequency of damper 160 is a function of radius 178 and angle 0. Theweight and surface area of masses 166, as well as the viscosity of fluid168, are factors which control energy dissipation of the damper.

FIGS. 7-10 show a further alternative embodiment of the instantinventive damper, designated as 110. This embodiment is constructed ofone or more modules 112 which have a plurality of interfittingintermediate trays 124 that fit and mate with bottom tray 114 and toptray 130 as will be described more fully hereinafter. Bottom tray 114'has a spherical section bottom 11-6 terminating at its outer edges inupwardly extending lower sidewall portion 118. Sidewall extensionconnects upper sidewall portion 122 to lower sidewall portion 118. Eachof trays 114, 124 and is of exactly the same construction wherein theouter dimension of lower sidewall portion 118 is equal to or slightlyless than the interior dimension of upper sidewall portion 122. Thisconstruction permits lower sidewall 118 to interfit within uppersidewall 122 and thereby permits assembly of a stack of interfittingtrays to form module 112.

Intermediate trays 124 have a plurality of apertures 126 in thehemispherical bottom thereof to permit com munication and flow of theviscous fluid, not shown, to flow between the various trays. Obviously,bottom tray 114 does not include such apertures in order to maintain thefluid tight relationship of module 112. Slugs 128 are disposed on theupper surface of the hemispherical bottoms of trays 114 and 124 and areshaped to have upper and lower surfaces substantially conforming to thearc of bottom 116 of the trays.

Top tray 130 also has at least two apertures 126 about which bosses 132are located. Threaded bores 134 in bosses 132 are located so as topermit communication with the interior of trays 124 and 114. Plugs 136are threaded to matingly engage threaded bores 134 and act o a n a n afluid tight modu e 112. At east two bosses,

132 and their attendant structure are necessary in order that a viscousfluid may be poured into one opening while the other provides a vent fordisplaced air. Module 112 is completed by providing fiberglass cover 138about a plurality of stacked trays to maintain module 112 fluid tightand an integral member.

Module 112 is further maintained as an integral assembly by the supportstructure for attaching damper 110 to the vibrating body. This mountingor supporting structure includes bottom ring 140 having a plurality ofapertures 142 peripherally spaced thereabout. The internal diameter ordimension of ring 140 is equal to or slightly greater than the externaldimension of lower sidewall portion 118. Spch dimensions permit bottomtray 114 to fit within and be supported by ring 140. Top plate 144 has aplurality of peripherally spaced apertures 148 and 150 therein. Plate144 overlies top tray 130 and is positively connected to ring 140 bybolts 152 extending through apertures 142 and 148. Nuts 154 matinglyengage bolts 152 to positively connect bottom ring 140 and top plate144.

The undersurface of top plate 144 has ring 146 extending therefrom. Ring146 has an outer dimension equal or slightly less than the internaldimension of top tray 130 to permit ring 146 to fit within tray 130 andthereby maintain an integral assembly for damper 110. Bosses 132 andring 146 are so dimensioned as to permit the positive assembly of damper110 Without interference by their encountering one another.

Referring to FIG. 8, apertures 148 and 150 are shown as spaced about topplate 144. As set forth hereinabove, apertures 148 are utilized forbolts 152 to maintain damper 110 integral. Alternate apertures 150 serveas a means for permitting damper 110 to be attached or mounted to thevibrating or oscillating body. FIG. 9 shows apertures 142 and 150 asalternately spaced about ring 140. Again alternate apertures 150 mayfunction to mount damper 110 to a vibrating body when necessary.Although damper 110 is shown herein as being of circular configurationin plan view, it is to be understood that substantially anyconfiguration in plan may be utilized without departing from the conceptof the instant invention.

Epoxy 156 is shown in FIG. 10 as providing an adhesive and seal betweenlower sidewall portion 118 and upper sidewall portion 122 ofinterfitting trays 114, 124 and 130. The instant invention does notcontemplate restriction or specific use of epoxy 156 and depending uponthe relative interfitting of adjacent trays it may be unnecessary toprovide any type of adhesive or seal to assist in maintaining anintegral assembly of module 112. It is to be noted that the structureshown in FIG. 10 is out of proportion in order to clarify the locationof seal material 156.

OPERATION Either of the viscous pendulum damper embodiments of theinstant invention would be attached to a primary structure which iseither being tested or in which there is some vibration displacement.When this primary structure to which the dampers are attachedexperiences acceleration, that is, an oscillatory or vibratory motion,the pendulum mass, having inertia, resists being accelerated. Theresistance of the pendulum to acceleration results in relative motionbetween the pendulum mass and the surrounding viscous medium causingenergy to be dissipated. The amount of energy dissipated is dependent onthe resistance force acting on the pendulum mass. If there is zeroresistance the net work dissipated per cycle of oscillation is zero. Onthe other hand, if there is infinite resistance such that the pendulummass is effectively frozen the mass does not move relative to theviscous medium and there is again zero net work dissipated per cycle.Consequently, it can be seen that there is some finite resistance ordamping force on the pendulous member for which maximum energydissipation occurs.

The value of this optimum resistance depends on the mode of operation ofthe damper which can either be tuned or untuned. For tuned operation thenatural frequency of the damper is approximately the same as that ofvibration frequency of the primary structure. For untuned operation itis implied that the pendulum natural frequency is very low relative tothe input vibration frequency of the primary structure. The dampingefficiency of a tuned viscous pendulum damper is much higher than thatof an untuned; however, in many practical applications where, forexample the input vibration occurs at relatively high frequencies orconsists of a continuous spectrum rather than discreet frequencies,untuned operation is preferred.

Viscous pendulum damper 10, see FIG. 1, is shown as having eightdisk-shaped slugs 26 and a tray assembly 20 containing eight trays 24. Alead slug 26 is placed on each of the trays and tray assembly 20inserted into container 16. Viscous fluid 28 is then poured intocontainer 16 and cover plate 34 secured in place by screws 38. Container16 may previously have been secured to a primary structure, for examplea test model in a Wind tunnel or such structures as smokestacks,antennas, bridges or drilling rigs, or it may be secured to such astructure subsequent to assembly. Once vibration damper 10 is secured tothe primary structure which is vibrating, the viscous fluid reacts withthe slugs to dissipate energy. Since the radius of curvatures of thetrays determines the natural frequency of the system the damper may 'bedesigned for either tuned or untuned operation as best suits thepurpose.

In the installation shown in FIGS. 1 and 2 the damper is designed foruntuned operation. That is, the natural frequency of the model orprimary structure to which this embodiment would be attached would beconsiderably greater than the pendulum frequency of the slugs. Normallyunder such circumstances the tray curvature provides essentially aself-centering feature for slugs 26. However, the damping ability ofviscous pendulum damper 10 may be readily varied by changing either thesize or the total number of slugs. By adding or removing slugs 26 thedamping can be varied in increments of approximately one-eighth themaximum damping with all eight slugs present. Thus, the dampingphenomenon closely follows the behavior predicted by the linear theoryfor viscous damping over a substantial range of vibration amplitudes.This feature makes the device particularly .attractive as a researchtool. For example, damper 10 may be attached to a test model and byvarying the number of slugs 26 the damping required to prevent excessivevibrations may be determined, thereby providing the data necessary forprotection of the primary structure from destructive oscillations.

The remotely controlled viscous pendulum damper shown in FIG. 3functions, in principle, in the same manner as multislug damper 10discussed previously. However, rather than removing or adding slugs tovary the damping, the pendulum mass in this case is varied bytransferring mercury or some other heavy liquid from bellows 86, rigidlyattached to damper case or container 62, to expansible bladder 72 whichis suspended as a pendulum in viscous fluid 92. Bellows 86 are connectedto and in communication with bladder 72 by flexible tube 74 whichconstrains bellows 86 to move in a pendulous path. The mass contained inbladder 72 is controlled by means of air pressure in actuator bellows84. This pressure is controlled by regulated pressure source 100 and isread on pressure gage 104 which assists in accurately setting thepressure in conduit 96 and therefore accurate determination of thepressure actuator bellows 84. The pressure in actuator bellows 84 actsagainst return spring which is of suflicient strength to collapsependulum bladder 72 when pressure is removed therefrom. As is evidentfrom FIG. 3, when remote control is unnecessary, bellows 84 and 86 couldbe operated by a local control, for example a screw threaded throughcover 64, acting thereagainst.

The quantity of mercury or other heavy liquid, and thus the damping ofthe system, can be calibrated against the pressure read on gage 104.Since the damper performance is dependent upon viscosity which isaffected by temperature, thermocouple 114 is utilized for accuratecalibration and, accordingly, is utilized with pressure gage 104 for anaccurate setting of diaphragm 88 and associated return spring 90.Viscous fluid 92 completely fills lower chamber 78 and by means oforifices 82 partially fills vented upper chamber 80 which is providedwith bafiies 94 to eliminate slosh motion of the damping fluid.

When the primary structure to which damper 60 is attached vibrates,pendulum bladder 72 reacts with viscous fluid 92 to dissipate energy andthereby damp the vibrations of the primary structure.

The alternative embodiment of the instant invention designated as damper110 operates substantially identically to the embodiment shown in FIGS.1 and 2. However, by utilizing a plurality of trays that interfit withone another it is possible to readily vary the number of trays andtherefor the number of slugs which determine the pendular mass and thusthe energy dissipating ability of the damper. Because bosses 132 are ofa depth permitting bottom trays 114 to interfit with top trays 130, aplurality of modules 112 may be assembled and even greater versatilityand variation of damping ability provided.

Damper 110 is formed by placing slugs 128 on the hemispherical bottoms116 of trays 114 and 124 and then stacking such trays until the sum ofthe masses of slugs 128 equal the mass necessary for damping theoscillations of the body to which damper 110 is to be secured. Top tray130 is then positioned on the top intermediate tray 124 and a viscousfluid is poured into the stacked trays via bores 134 and flows from onetray to the next by means of apertures 126 with the displaced air beingvented through the opposite bore 134. Plugs 136 are then threaded intobores 134 and module 112 is fluid tight. In order to further theintegral relationship of trays 114, 124 and 130 fiberglass cover 138 isthen put around the assembled unit. Module 112 is then placed on ring140 and top plate 144 put in position and nuts 154 threaded on bolts 152to provide positive connection and insurance of integrity of module 112.Damper 110 would then be mounted on the oscillating structure by anydesired means, for example, by utilizing apertures 150 in either topplate 144 or bottom ring 140.

Damper 160, shown in FIGS. 46 also functions as previously describedembodiments in that tubes 162 form approximately the arc of a circle andsupport spheres 166 for pendular movement in viscous fluid 168. Oncespheres 166 are in place and viscous fluid 168 is poured into containers162 via valve 176, damper 160 is mounted upon vibrating body 172 bysupports 16-4. The oscillatory motion of body 172 causes sphericalmasses 166 to move as constrained along the are established by container162 to act against fluid 168 and thereby dissipate energy and overcomethe oscillatory forces of body 172. Again it is to be noted that theembodiment of the invention shown in FIGS. 46 is cylindrical but theinvention does not contemplate such a limitation and it is to beunderstood that any configuration of body 172 may fit within the abilityof damper 160 to suppress oscillations thereof.

In view of the above discussed features of the instant invention, it isreadily apparent that there is a multitude of potential applicationsincluding reduction of wind induced vibration on full scale structuressuch as rocket launch vehicles, smokestacks, large antennas, bridges anddrilling rigs; elimination of wake induced oscillations of submarineperiscopes; and protection of machines, instruments or equipment fromexcessive vibrations, as Well as serving s time saver in ests being runn t cili ies re- 8 quiring a pumping cycle each time an entry is madeinto the test section.

From the above it is readily apparent that the instant inventionprovides the advantages of linear damping characteristics, bidirectionaloperation, and precise regulation of damping for either tuned or untunedoperation. The instant invention also does away with the problemscommonly associated with tuned spring mass dampers having spring stressproblems and saves time in research studies while not requiring guywires or external connections for damping which avoids aerodynamicproblems associated therewith. Further, the device of the instantinvention is a simple inexpensive way of providing remotely controlleddamping means.

Obviously, many modifications and variations of the subject inventionare possible in the light of the above teachings.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a viscous pendulum damper the combination comprising: a container;variable mass pendulum means mounted in said container; means forvarying the mass of said pendulum means; control means for operatingsaid means for varying the mass of said pendulum means; and a viscousfluid in said container covering said pendulum means whereby the mass ofsaid pendulum means may be varied to alter the damping characteristicsof the damper.

2. The viscous pendulum damper of claim 1 wherein said control means arelocated remotely from said container and are interconnected therewith byconduit means.

3. The damper of claim 1 wherein said pendulum means comprises a bladderflexibly mounted in said container.

4. The damper of claim 1 wherein said container comprises upper andlower chambers interconnected by orifices to compensate for variation ofthe mass of said pendulum means.

5. The damper of claim 1 wherein a divider is secured within saidcontainer for separation thereof into upper and lower chambers; andorifices in said divider to provide communication between said chambers.

6. The dam-per of claim 1 wherein the means for expanding the pendulummeans comprises actuator bellows and fluid filled bellows separated by adiaphragm.

7. The damper of claim 6 wherein spring means are located in said fluidfilled bellows for returning said diaphragm to a neutral position; andsaid fluid filled bellows rigidly attached to said container.

8. The damper of claim 7 wherein said pendulum means comprises a bladderflexibly mounted in said contamer.

9. The damper of claim 8 wherein a divider having a plurality oforifices is secured within said container to form upper and lowerchambers; and said bladder flexibly mounted on said divider to protrudeinto said lower chamber.

10. The damper of claim 9 wherein said fiuid fills said lower chamberand a portion of said upper chamber; and baffles in said upper chamberfor eliminating slosh motions of said fluid.

11. The damper of claim 10 wherein said control means is locatedremotely from said container and connected to said actuator bellows by aconduit having a pressure gage operably attached thereto.

12. The damper of claim 11 wherein a thermocouple is mounted in saidlower chamber of said container to permit calibration of damping bycoordination of temperature and pressure.

13. A viscous pendulum damper comprising: tubular container means havinga plurality of scalloped sections; each of the scallop sections of saidcontainer means substantially conforming to a segment of a circular arc;a plurality of masses disposed in said scalloped sections f r p u armoveme a. vi o s flu d substan ia y fill- 9 10 ing said container; andmeans which support said con- 2,028,197 1/1936 Dunning. tainer from theoscillating body, Where variation of the 2,656,742 10/1953 Poole.viscosity of the fluid, of the mass of the spherical masses 3,113,64012/1963 Stedman. and of the number of tubular elements in the containermeans alter the damping characteristics and permit cali- 5 DUANE REGER,Primary Examiner bration of the damper.

US. Cl. X.R. References Cited UNITED STATES PATENTS 1,700,477 1/1929Goode. 10

